Aspergillus spp. are seed deteriorating fungi known for their ability to produce mycotoxins in crops. Typically, the mycotoxins produced by Aspergillus spp. during colonization are aflatoxin and sterigmatocystin. Both aflatoxin and sterigmatocystin are derived from polyketides, which are bioreactive secondary metabolites that are synthesized like fatty acids.
Infection of crops by Aspergillus spp. is highly undesirable since aflatoxin and the related mycotoxin sterigmatocystin are human carcinogens. In certain years, environmental conditions heavily favor the production of mycotoxins. Thus, it is necessary to survey food products and feeds for such contamination of mycotoxins. Contaminated supplies in the United States are typically destroyed. In developing countries, where governments cannot afford to screen and destroy contaminated food, high liver cancer rates are associated with mycotoxin contamination. Thus, methods are needed to control mycotoxin contamination in foods.
In addition to fungi, diseases in plants are caused by viruses, bacteria, and nematodes. Phytopathogenic fungi cause significant annual crop yield losses as well as devastating epidemics. Plant disease outbreaks have resulted in catastrophic crop failures that have triggered famines and caused major social change. Pathogenic fungi attack all of the approximately 300,000 species of flowering plants; however, a single plant species can be host to only a few fungal species, and similarly, most fungi usually have a limited host range. Generally, the best strategy for plant disease control is to use resistant cultivars selected or developed by plant breeders for this purpose. However, the potential for serious crop disease epidemics persists today, as evidenced by outbreaks of the Victoria blight of oats and southern corn leaf blight. Molecular methods of crop protection have the potential to implement novel mechanisms for disease resistance and can also be implemented more quickly than traditional breeding methods. Accordingly, molecular methods are needed to supplement traditional breeding methods to protect plants from pathogen attack.
A host of cellular processes enable plants to defend themselves against disease caused by pathogenic agents. These defense mechanisms are activated by initial pathogen infection in a process known as elicitation. In elicitation, the host plant recognizes a pathogen-derived compound known as an elicitor; the plant then activates disease gene expression to limit further spread of the invading microorganism. It is generally believed that to overcome these plant defense mechanisms, plant pathogens must find a way to suppress elicitation as well as to overcome more physically-based barriers to infection, such as reinforcement and/or rearrangement of the actin filament networks near the cell's plasma membrane.
Thus, the present invention solves needs for enhancement of the plant's defensive elicitation response via a molecularly based mechanism that can be quickly incorporated into commercial crops.